ABSTRACT

Our objectives were to isolate bovine stromal-vascular cells using explants and to determine media components that promote differentiation into mature adipocytes for studies of lipogenic enzyme regulation. Stromal-vascular cells were grown from explants and treated with differentiation media for 8 d after reaching confluence. Differentiation was assessed by measuring radiolabeled acetate incorporation into lipids, glycerol-3-phosphate dehydrogenase activity, and the mRNA expression of fatty acid binding protein-4, PPAR-γ, and acetyl-CoA carboxylase-α (ACCα). After 8 d of differentiation, medium containing 10 μg/mL of insulin, 0.25 μM dexamethasone, 0.5 mM isobutylmethylxanthine, 1 mM octanoate, and 2% Intralipid (Fisher Scientific, Suwanee, GA) produced greater acetate incorporation (P < 0.001) and glycerol-3-phosphate dehydrogenase activity (P < 0.001) compared with other media tested. This differentiation medium also increased mRNA expression of fatty acid binding protein-4, PPARγ, and ACCα by 180-, 7-, and 3-fold, respectively, compared with undifferentiated control cells (P < 0.05). To further improve the differentiation protocol, the effects of Intralipid, rosiglitazone, and troglitazone were examined. Removal of 2% Intralipid did not improve any differentiation measures. Addition of rosiglitazone (1 μM), a PPAR-γ agonist, increased acetate incorporation and ACCα mRNA (P < 0.01). Addition of troglitazone (5 μM), another PPAR-γ agonist, increased acetate incorporation to a similar extent as rosiglitazone and produced the greatest expression of ACCα mRNA (P < 0.01), but was not superior to medium that included rosiglitazone for any other differentiation measures. Cell-seeding density influences the cell divisions required to reach confluence, and increased plating density (2 × 10⁴ cells/cm² vs. 6.7 × 10³ cells/cm²) increased acetate incorporation by 100% (P < 0.001). Differentiating stromal-vascular cells in the presence of trans-10, cis-12 CLA inhibited differentiation of stromal-vascular cells into mature adipocytes, reducing radiolabeled acetate incorporation into lipids (P < 0.001), stearoyl-CoA desaturase-1 mRNA (P < 0.05) and protein abundance (P < 0.05), and ACCα protein abundance (P < 0.05). We have developed a method to differentiate primary bovine adipocytes, which will allow us to study the regulation of lipogenic enzymes by nutrient and endocrine factors.

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Copyright © 2010. American Society of Animal Science.